Simplified sewerage is an important sanitation option in peri-urban areas of developing countries, especially as it is often the only technically feasible solution in these high-density areas.
4.7 / P 0.11 (P is estimated population equivalent in thousand)
Hydraulic Design 1. Minimum Velocity 2. Maximum Velocity 3. Minimum Depth of Invert 4. Minimum Size of Sewer 5. Minimum Size of Laterals
= 0.8 m/s = 4.0 m/s = 1.5 m = 225mm VCP = 150mm VCP
Manholes 1. Distance between Manholes Maximum 100m for sewer up to 225 mm diameter 2. Location of Manholes Upstream end of all sewer Every change in direction Every change in gradient Every change in size of sewer All intersection and junction
Materials Vitrified Clay Pipe (VCP) – Sewers up to 225 mm diameter
METHOD OF CALCULATION 1. Design for Sewerage Flow Rate Peak Flow, Q peak
= Average flow, Q average x Peak Flow Factor = Q average x 4.7 / P 0.11
(NOTE: P is population Equivalent in Thousand)
2. Flow Data in Verified Clay Pipe From Manning’s Formula, V = 1/n R 2/3 S 1/2
------------------------ (1)
From Continuity Equation. Q=VA
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Applying (1) into (2) Q = (1/n R 2/3 S ½) A Where
V = velocity (m/s) R = hydraulic radius (m) S = gradient Q = capacity (m3/s) A = cross-sectional area of pipe (m2) n = Manning’s coefficient (0.013 for VCP)
